Adds a MastodonClient trait

This is useful for user code, which can use the trait to add a layer of
indirection to their code, allowing them to swap out implementations for
testing

examples/follow_profile.rs

@@ -1,5 +1,6 @@
 mod register;
 
+use register::MastodonClient;
 use std::error;
 
 fn main() -> Result<(), Box<error::Error>> {

examples/print_your_profile.rs

@@ -1,7 +1,9 @@
 mod register;
 
+use register::MastodonClient;
 use std::error;
 
+
 fn main() -> Result<(), Box<error::Error>> {
     let mastodon = register::get_mastodon_data()?;
     let you = mastodon.verify_credentials()?;

examples/register.rs

@@ -1,6 +1,8 @@
 extern crate mammut;
 extern crate toml;
 
+pub use self::mammut::MastodonClient;
+
 use std::{
     error::Error,
     fs,

examples/search.rs

@@ -1,5 +1,6 @@
 mod register;
 
+use register::MastodonClient;
 use std::error;
 
 fn main() -> Result<(), Box<error::Error>> {

examples/upload_photo.rs

@@ -1,5 +1,6 @@
 mod register;
 
+use register::MastodonClient;
 use std::error;
 
 fn main() -> Result<(), Box<error::Error>> {